Studies on a novel anion-exchange membrane based on chitosan and ionized organic compounds with multiwalled carbon nanotubes for alkaline fuel cells

Robust anion exchange membranes based on ionic liquid grafted chitosan/polyvinyl alcohol/quaternary ammonium functionalized silica for polymer electrolyte membrane fuel cells

In this study, 1-bromohexyl-1methylpiperidinium bromide (Br-6-MPRD) ionic liquid grafted quaternized chitosan (QCS) and polyvinyl alcohol (PVA) blends were composited with glycidyl trimethyl ammonium chloride (GTMAC) quaternized silica (QSiO2) at different dosages. Glutaraldehyde (GA) crosslinked the membranes and then processed into hydroxide form with an aqueous potassium hydroxide solution. The resultant IL-QCS/PVA/QSiO2 membranes exhibit significantly improved ionic conductivity, moderate water absorption and swelling ratio compared with the pristine IL-QCS/PVA anion exchange membrane (AEM). Among them, the hydroxide ion conductivity and power density of IL-QCS/PVA/QSiO2-7 membrane can reach up to 78 mS cm-1 at 80 °C and 115 mW cm-2 at 60 °C respectively. In addition, IL-QCS/PVA/QSiO2 membranes have excellent thermal, mechanical, and chemical stabilities, which can meet the application requirements of AEM for fuel cells.

High performance chitosan/nanocellulose-based composite membrane for alkaline direct ethanol fuel cells

Polysaccharide anion exchange membranes (AEMs) containing chitosan (CS), cellulose nanofibrils (CNFs) and CNFs quaternized with poly(diallyldimethylammonium chloride) (CNF(P)s) were developed for use in alkaline direct ethanol fuel cells (ADEFCs). The resulting composite membranes prepared by the solvent casting process based on an experimental design were comprehensively assessed for morphology, KOH uptake, swelling ratio, EtOH permeability, mechanical properties, ionic conductivity, and cell performance. The fabricated CS-based composite membranes with CNF(P) fillers were superior to the commercial Fumatech FAA-3-50 membrane in terms of Young's modulus and tensile strength (69 % and 85 % higher, respectively), ion exchange capacity (169 % higher), and ionic conductivity (228 % higher). Single fuel cell tests have shown excellent performance of the CS-based membranes with CNF and CNF(P) fillers, as they exhibited up to 86 % improvement in power density at 80 °C compared to the commercial membrane (65.1 mW/cm2 vs. 35.1 mW/cm2) and higher maximum power density at all test conditions.

Dual reinforced composite membranes from in-situ ionic crosslinked quaternized chitosan filled quaternized polyvinylidene fluoride nanofiber for alkaline direct methanol fuel cell

The main obstacle of high-performance cationic functionalization chitosan (CS) as anion exchange membranes (AEMs) is the trade-off between mechanical stability and ionic conductivity. Here, in-situ ionic crosslinking between the deprotonated hydroxyl group and quaternary ammonium group under alkaline conditions was ingeniously applied to improve the mechanical stability of highly quaternized CS (HQCS) with high IEC (>2 mmol g-1). Meanwhile, to further reduce the swelling and enhance the hydroxide conductivity, a mechanically robust hydroxide ion conduction network, quaternized electrospun poly(vinylidene fluoride) (QPVDF) nanofiber, was subsequently used as the filling substrate of in-situ crosslinked HQCS to prepare dual reinforced thin AEMs. The introduction of a robust QPVDF nanofiber mat can not only greatly improve the mechanical properties and limit swelling, but also create facile ion transport channels. Notably, the HQCS/QPVDF-74.0 composite membrane demonstrates perfect dimensional stability, high mechanical performance and excellent alkaline stability, as well as superior ionic conductivity of 66.2 mS cm-1 at 80 °C. The thus assembled alkaline direct methanol fuel cell displays a maximum power density of 132.30 mW cm-2 using 5 M KOH and 3 M methanol as fuels at 80 °C with satisfactory durability.

Efficiency of Neat and Quaternized-Cellulose Nanofibril Fillers in Chitosan Membranes for Direct Ethanol Fuel Cells

In this work, fully polysaccharide based membranes were presented as self-standing, solid polyelectrolytes for application in anion exchange membrane fuel cells (AEMFCs). For this purpose, cellulose nanofibrils (CNFs) were modified successfully with an organosilane reagent, resulting in quaternized CNFs (CNF (D)), as shown by Fourier Transform Infrared Spectroscopy (FTIR), Carbon-13 (C13) nuclear magnetic resonance (¹³C NMR), Thermogravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC), and ζ-potential measurements. Both the neat (CNF) and CNF(D) particles were incorporated in situ into the chitosan (CS) membrane during the solvent casting process, resulting in composite membranes that were studied extensively for morphology, potassium hydroxide (KOH) uptake and swelling ratio, ethanol (EtOH) permeability, mechanical properties, ionic conductivity, and cell performance. The results showed higher Young's modulus (119%), tensile strength (91%), ion exchange capacity (177%), and ionic conductivity (33%) of the CS-based membranes compared to the commercial Fumatech membrane. The addition of CNF filler improved the thermal stability of the CS membranes and reduced the overall mass loss. The CNF (D) filler provided the lowest (4.23 × 10^-5 cm² s^-1) EtOH permeability of the respective membrane, which is in the same range as that of the commercial membrane (3.47 × 10^-5 cm²s^-1). The most significant improvement (~78%) in power density at 80 °C was observed for the CS membrane with neat CNF compared to the commercial Fumatech membrane (62.4 mW cm^-2 vs. 35.1 mW cm^-2). Fuel cell tests showed that all CS-based anion exchange membranes (AEMs) exhibited higher maximum power densities than the commercial AEMs at 25 °C and 60 °C with humidified or non-humidified oxygen, demonstrating their potential for low-temperature direct ethanol fuel cell (DEFC) applications.

A Review of Recent Chitosan Anion Exchange Membranes for Polymer Electrolyte Membrane Fuel Cells

Considering the critical energy challenges and the generation of zero-emission anion exchange membrane (AEM) sources, chitosan-based anion exchange membranes have garnered considerable interest in fuel cell applications owing to their various advantages, including their eco-friendly nature, flexibility for structural modification, and improved mechanical, thermal, and chemical stability. The present mini-review highlights the advancements of chitosan-based biodegradable anion exchange membranes for fuel cell applications published between 2015 and 2022. Key points from the rigorous literature evaluation are: grafting with various counterions in addition to crosslinking contributed good conductivity and chemical as well as mechanical stability to the membranes; use of the interpenetrating network as well as layered structures, blending, and modified nanomaterials facilitated a significant reduction in membrane swelling and long-term alkaline stability. The study gives insightful guidance to the industry about replacing Nafion with a low-cost, environmentally friendly membrane source. It is suggested that more attention be given to exploring chitosan-based anion exchange membranes in consideration of effective strategies that focus on durability, as well as optimization of the operational conditions of fuel cells for large-scale applications.

Anion Exchange Membranes with 1D, 2D and 3D Fillers: A Review

Hydroxide exchange membrane fuel cells (AEMFC) are clean energy conversion devices that are an attractive alternative to the more common proton exchange membrane fuel cells (PEMFCs), because they present, among others, the advantage of not using noble metals like platinum as catalysts for the oxygen reduction reaction. The interest in this technology has increased exponentially over the recent years. Unfortunately, the low durability of anion exchange membranes (AEM) in basic conditions limits their use on a large scale. We present in this review composite AEM with one-dimensional, two-dimensional and three-dimensional fillers, an approach commonly used to enhance the fuel cell performance and stability. The most important filler types, which are discussed in this review, are carbon and titanate nanotubes, graphene and graphene oxide, layered double hydroxides, silica and zirconia nanoparticles. The functionalization of the fillers is the most important key to successful property improvement. The recent progress of mechanical properties, ionic conductivity and FC performances of composite AEM is critically reviewed.

Review of Chitosan-Based Polymers as Proton Exchange Membranes and Roles of Chitosan-Supported Ionic Liquids

Perfluorosulphonic acid-based membranes such as Nafion are widely used in fuel cell applications. However, these membranes have several drawbacks, including high expense, non-eco-friendliness, and low proton conductivity under anhydrous conditions. Biopolymer-based membranes, such as chitosan (CS), cellulose, and carrageenan, are popular. They have been introduced and are being studied as alternative materials for enhancing fuel cell performance, because they are environmentally friendly and economical. Modifications that will enhance the proton conductivity of biopolymer-based membranes have been performed. Ionic liquids, which are good electrolytes, are studied for their potential to improve the ionic conductivity and thermal stability of fuel cell applications. This review summarizes the development and evolution of CS biopolymer-based membranes and ionic liquids in fuel cell applications over the past decade. It also focuses on the improved performances of fuel cell applications using biopolymer-based membranes and ionic liquids as promising clean energy.